To express the value of the arc secant of the square root of 2 you must first express its cross multiplication process that having variable x as its total then you will came up with sec(x) =sqrt(2) then remember that sec() is equals to 1/cos(x), then its is 1/cos(x) = sqrt(2) then use the special triangle principles withe side length of 1,1 and sqrt(2) and the value of that is pi/4 so x= pi/4 then arcsec(sqrt(2)) = pi/4.